Heat sensitive copying sheet

ABSTRACT

HEAT SENSITIVE COPYING PAPERS USING A SPIRO COMPOUND HAVING THE FORMULA A   2-R1,2&#39;&#39;-R2-3,3&#39;&#39;-SPIROBI(3H-NAPHTHO(2,1-B)PYRAN   WHEREIN R1 AND R2 EACH IS SELECTED FROM THE GROUP CONSISTING OF A HYDROGEN ATOM, AN ALKYL GROUP HAVING FROM 1 TO 8 CARBON ATOMS, A CARBOXYLIC ACID ESTER, AN ARALKYL GROUP AND A PHENYL GROUP, A SOLID ORGANIC SULFONIC ACID HAVING THE FORMULA   R-SO3H (B)   WHEREIN R IS SELECTED FROM THE GROUP CONSISTING OF AN AMINO GROUP, AN N-SUBSTITUTED AMINO ALKYL GROUP HAVING FROM 2 TO 18 CARBON ATOMS, AN UNSUBSTITUTED AMINO ALKYL GROUP HAVING FROM 2 TO 18 CARBON ATOMS, AN ALKYL GROUP HAVING FROM 10 TO 20 CARBON ATOMS, AN ALKOXY GROUP HAVING FROM 10 TO 20 CARBON ATOMS, A CARBOXYLIC ACID SUBSTITUTED ALKYL GROUP, SAID ALKYL GROUP HAVING FROM 6 TO 18 CARBON ATOMS, AND AN AROMATIC RING, AND A THERMOFUSIBLE MATERIAL HAVING A MELTING POINT RANGING FROM 50 TO 180*C. ARE DISCLOSED.

United States Patent 01 7 3,666,525 Patented May 30, 1972 lice-3,666,525 HEAT SENSITIVE COPYING SHEET Shiro Kimura, Teruo Kobayashi,and Sadao Ishige, Kanagawa, Japan, assignors to Fuji Photo Film Co.,Ltd., Minami-ashigara-machi, Kanagawa, Japan No Drawing. Filed May 26,1970, Ser. No. 40,732 Claims priority, application Japan, May 26, 1969,44/ 40,719 Int. Cl. B41m /18 US. Cl. 117-363 17 Claims ABSTRACT OF THEDISCLOSURE Heat sensitive copying papers using a spiro compound havingthe Formula A wherein R and R each is selected from the group consistingof a hydrogen atom, an alkyl group having from 1 to 8 carbon atoms, acarboxylic acid ester, an aralkyl group and a phenyl group, a solidorganic sulfonic acid having the Formula B BACKGROUND OF THE INVENTION(1) Field of the invention The present invention relates to a heatsensitive copying sheet.

(2) Description of the prior art Many heat sensitive copying sheets arewell known. However, above all, one having a layer comprising twocolorless solid compounds contacting with each other to cause thereaction of color development and a thermofusible material on a supportis general. The coloration mechanism of this heat sensitive copyingsheet is as follows:

When this sheet is superposed on an original drawing and heated orirradiated with an infra-red ray, the image of the character on theoriginal drawing is preferentially raised in temperature and thethermofusible material of the part fuses the two colorless compounds.Then the two fused compounds react to develop color. One of the twocolorless compounds includes crystal violet lactones and benzo indolinospiropyrans, and another includes, for example, clays, such as acidclay, zeolite, kaolin, attapulgite, and the like; mineral acids, such ashydrochloric acid, sulfuric acid, perchloric acid, phosphoric acid, andthe like; organic acids, such as benzoic acid, p-chlorobenzoic acid,gallic acid, phthalic acid, salicylic acid, oxalic acid, maleic acid,citric acid, stearic acid, and the like; and phenols, such asp-butylphenol, p-phenylphenol, a-naphthol, catechol, resorcinol, and thelike.

However, these heat sensitive copying sheets sufier from thedisadvantages that a color development fog is formed before heating, thepreservation of the developed color image, such as the light resistance,resistance to water, and the like, is poor, and the sheets are notdeveloped in color the instant they are heated, and the like, becausethe two compounds are coated on the support in contact with each other.As a result, an excellent heat sensitive copying sheet has been desired.

Therefore, an object of the present invention is to provide a heatsensitive copying sheet in which such color development fog is notformed before heating and develops color instantly on heating. Thedeveloped color image is excellent in light resistance and resistance towater.

SUMMARY OF THE dNVEN'I ION The present inventors have found that theabove object is attained by combining a spiro compound and an organicsulfonic acid.

More specifically, the heat sensitive copying sheet of this invention isone having a spiro compound, represented by Formula A wherein R and Reach is a hydrogen atom, an alkyl group having from .1 to 8 carbonatoms, a carboxylic acid ester, an aralkyl group, or a phenyl group, asolid organic sulfonic acid, represented by the Formula B DETAILEDDESCRIPTION OF THE INVENTION The general process for preparing the heatsensitive copying sheet of the present invention is as described below.

A nearly colorless spiro compound, an organic sulfonic acid and athermofusible material, as described above, are sufliciently mixed in asolution or suspension of a binder in an organic solvent or water, andcoated on a support such as paper, natural or synthetic resin films, andthe like, and dried. The above liquid mixture can be combed into thesupport. Also, on mixing, an opacifying agent can be added and mixedtherein. The heat sensitive copying sheet of the present invention isnot limited to this technique. For example, the abovementioned spirocompound and the thermofusible material can be mixed in the bindersolution, and alternatively the organic sulfonic acid and thethermofusible material can be mixed in the binder solution, and thenboth solutions can be mixed and coated on a support, or the formersolution may be coated on the support and then the latter solution maybe coated thereon.

The amount of each component to be used for producing the heat sensitivecopying sheet of the present invention is from 1 to 2. parts by weightof the spiro compound (the Formula A); from 1 to 6 parts by weight ofthe organic sulfonic acid (the Formula -B); from 3 to 30 parts by weightof the thermofusible material; from 3 to 15 parts by weight of thebinder; and from 20 to 300 parts by weight of solvent.

Examples of the spiro compounds represented by the 19. CH COGHC s labove Formula A are shown in the following table: 3 2 O Color developingMelting agent R" R point, 0. Name I H H 258 2,igpirogflbenzo[f]chromene)J. Chem. 500.,

27,1 II CH3 H 203 3-Inethy1-2,2-spirobi(benzolflchromene) J.

Pract. Chem.,[2] 114, 190 Ben, 59, 1381. III CH(CH1); H 2043-iso-propyl-2,2'-spirobi(benz0[f]ch1omene) J.

Chem. 300., 1929, 942. IV 05H 11 1823-zgin3gg,2'-spirobi(benzolflchromene) Ben, V CsHu H 1573-ocyl-2;2-spir0bi(benzo[f]ehromene) J. Chem.

500., 1929, 937. VI CH; CH; 2383,3-dimethyl-2,2-spirobi(benzoIflchromene) J.

Chem. 800., 1927, 1703 Ber., 61, 967. VII CO 0 01H; CO QCzHs 205207 3,3-dica.rboethoxy-2, 2-spirobi(b nzolflchronxene) J Chem. 300., 1927,1703. VIII H 207 3-benzyl-2,2'-splrobi(benzo[i]chromene) Ben,

CHz- .59. 1382.

IX CH2-CHz- H 210-220 3-phenylethyl-2,2spirobl(benzomchromene) J.

Chem. $00., 1931, 1336.

X H 240 3-phenyl-2, 2'-sip10bl(benzolflchromene) Ben,

These compounds are almost colorless crystals.

These spiro compounds can be prepared by condensing Q-NH-Q-SO H2-hydroxyl-l-napthoaldehyde with the respective corresponding ketones asdescribed in the literature references.

NOH Next, the orgamc sulfomc aclds represented by the Formula B can beexemplified as follows: 0= 5 S 0 1. NHzSOaH 21 2. Nmcmoms 03H(0211.5)2NQ 3. CHr-CH:

o N CHCHOHCHSOH 03H 2 2 2 a a i 23. 02155 our-0H, 3o

4. H N -s0 11 Q-NHCHrGH S 03H 2 3 6 H 5. (CHahNCHzCHzC H25 03H 2 2 B 6.016111150111 40 CH Q-SOzl-I 7. GMHnS B 8. C11H2OSO5H NH! 9. CrsHgzOSOaH25. 10. C1aHaafi rH HZN SOSH l C OOH 00211. 11. omuofisoan m o 0011OH2CONHQ-SO3E 12. I

CHaCH2SO H CH3 27. Q HO ooQ-Mm HO-U-OILS 03H 28 H0 0 c l 14. H1o-c=o@4031;

\N l N02 Q 803E HO S03H 16. NH;- 30. OH

11o-so.11

SOQH 18. 1

H088 SOaH These compounds are almost colorless solids.

Suitable thermofusible materials are acetanilide, urea, diphenylamine,diphenyl, naphthalene, benzoin, anaphthol, fi-naphthol, para-t-butylphenol, para-phenylphenol, 4,4'-cyclohexyiidene diphene diphenol,4,4-isopropylidene diphenol, phthalic anhydride, maleic anhydride,stearic acid, benzoic acid, a-naphthyl acetic acid, methylpara-hydroxybenzoate, diphenyl phthalate, triphenyl phosphate,para-hydroxydiphenyl ether, and the like.

These compounds are colorless or lightly colored solids at ordinarytemperatures of lower than 50 C. and have sharp melting points near thetemperature suitable as the heating temperature for copying, that is,from 50 to 180 0., and dissolve the above spiro compounds (the FormulaA) and the organic sulfonic acids (the Formula B) in the fused state.The above three components are not necessarily used on or in the samesupport, and one or two of said components can be used on two separatesupports.

The binders to be used in the present invention are ex emplified bystyrene-butadiene copolymers, alkyd resins, polybutylmethacrylates,vinyl chloride-vinyl acetate copolymers, styrene maleic anhyridecopolymers, synthetic rubbers, gum arabic, polyvinyl alcohol,hydroxyethylcellulose, and the like.

These materials bind the above spiro compounds (the Formula A) and thethermofusible materials and not easily discolored on heating. They canbe used alone or in combination.

The solvents to be used in the present invention are examplified byorganic solvents such as benzene, toluene, hexane, xylene, ligroin,acetone, ethyl acetate, and the like; and water.

These solvents are used to dissolve the above binders or as dispersionemulsions, and are finally distilled off.

In general, with organic sulfonic acids having an amino group in theFormula B, an organic solvent or water may be optionally used. Withorganic sulfonic acids not having an amino group or ones easily solublein an organic solvent, water is preferable. With organic sulfonic acidseasily soluble in water, use of water is allowed. This appears to resultfrom the lack of solubility of the coupler represented by the Formula Ain water.

Pacifying agents which can be used in the present invention areexemplified by titanium oxide, zinc oxide, barium sulfate, calciumsulfate, starch and the like.

The heat sensitive copying sheet of this invention has the advantagesthat a color development fog is not formed during the preparation andduring the period after drying and before heating even though thecompounds of the Formulas A and B are in contact with each other, that,even if the sheet is exposed before copying color develop ment, it isgood in stability during the lapse of time without any lowering of thecolor developing ability, and that, when copying using a heatsensitivecopying machine, the copied part develops color instantly and thedeveloped color is good in light resistance and resistance to Water.

When substituting phenols, such as, for example, parabutyl phenol,para-phenylphenol, a-naphthol, catechol, resorcinol, 2,2'-methylene-bis(4-chlorophenol), 4,4-iso propylidine diphenol, and the like for thecompounds represented by the Formula B, the sheet does not develop coloreven on; heating, and thus is not practical. Substituting benzoic acid,parachlorobenzoic acid, gallic acid, phthalic acid, salicylic acid,oxalic acid, maleic acid, citric acid, stearic acid, and the like, forthe compounds represented by the Formula B, the sheet is hardlydeveloped color even on heating, has no contrast, and is poor in lightresisting property, and this is not practical. When active clays suchas, for example, acid clay, zeolite, kaolin, attapulgite, and the like,or mineral acids such as, for example, hydrochloric acid, sulfuric acid,perchloric acid, phosphoric acid, and the like, are used, the sheet hasthe disadvantage of forming a color development fog during mixing in thesolvent and immediately after coat ing and drying.

When crystal violet lactone and benzo indolino spiropyrans aresubstituted for the compounds represented by the Formula A, the sheetdevelops a fog color all over the surface at the time of copyingprinting, and is poor in light resistance. The combinations of couplersand acids, which are used in the present invention, have overcome thesedisadvantages.

The present invention will be illustrated further by reference to thefollowing examples:

Example 1.35 g. of coupler No. I, 31 g. of organic sulfonic acid No. 17,39 g. of acetanilide, 120 g. of styrenebutadiene copolymer, and 1200 g.of toluene were mixed and ground in a ball mill for 2 days. The solutionmixture was coated on a paper and dried at 40 C. to obtain a heatsensitive copying sheet. This sheet was superposed on an originaldrawing and heated by means of a heat sensitive copying machine(manufactured by Thermofax Secretary 3M Co.) to obtain a blue-violetimage. The copied image was exposed to sunlight for 20 hours. As theresult, the developed color image was not lowered in concentration atall and undeveloped portion, i.e. non-image part, remained white as itwas initially and was not changed. That is the light resistance wasexcellent. Even on allowing the sheet to stand at a temperature of 50 C.and a relative humidity of for 20 hours, or even on wettingit with waterimmediately after it was obtained, the concern tration of the colordeveloped image was not lowered. That is, resistance to water wasexcellent.

0n the other hand, a heat sensitive copying sheet was prepared usingcrystal violet lactone (a known coupler), gallic acid an organic acid),acetanilide (a thermofusible material), a styrene-butadiene copolymer (abinder) and toluene (a solvent) in the same manner as described above.The heat sensitive copying sheet was heated in the same manner asdescribed above to obtain a blue-violet image. The image faded anddisappeared in the test for light resistance and resistance to waterunder the same condition as described above.

On substituting 3-chloro-sulfanilic acid (organic sulfonic acid No. 17)for gallic acid, the light resistance and resistance to water weresimilarly poor.

Also, on using 1,3,3-trimethyl8'-methoxy-indoline-benzospiropyran (aknown coupler) and 4,4'-isopropylidiue diphenol (both as an organic acidand a thermofusible material), the light resistance was poor, and evenon using organic sulfonic acid No. 17 together therewith, the lightresistance was poor.

Example 2.35 g. of coupler No. II, 70 g. of organic sulfonic acid No.57,500 g. of ,S-naphthol and 800 g. of ligroin were mixed and ground ina ball mill for 1 day. Subsequently, g. of a styrene-butadiene copolymerand 800 g. of toluene were added thereto and mixed and ground for 2hours. The solution was coated on a film and dried at 40 C. to obtain aheat sensitive copying sheet. The sheet was superposed on an originaldrawing and heated by means of a heat sensitive copying machine(trademark: *Risofax; manufactured by Riso Kagaku Co., Ltd.) to obtain ablue image which was similarly excellent as in Example 1 in lightresistance and resistance to water.

Example 3.50 g. of coupler No. IH, 300 g. of urea and 600 g. of acetonewere mixed and ground in a ball mill for 2 days. On the other hand, 30g. of organic sulfonic acid No. 8, 300 g. of urea, 200 g. ofpolybutyl-methacrylate, and 600 g. of ethyl acetate were mixed andground in a ball mill. The ground materials were mixed and furthertreated in a ball mill for 5 hours. The resulting mixture, thus treated,was coated on a support and dried to obtain a heat sensitive copyingsheet. The sheet was heated in the same manner as in Example 1 to obtaina blue image. The light resistance and resistance to water of the imagewere similarly excellent as in Example 1.

Example 4.l g. of coupler No. IV, 20 g. of organic sulfonic acid No. 36,200 g. of stearic acid, 70 g. of styrenemaleic anhydride copolymer and2000 g. of xylene were treated in the same manner as in Example 1 toobtain a heat sensitive copying sheet. The sheet was heated in the samemanner as in Example 1 to obtain a blue image. In case of the omissionof the organic sulfonic acid, the color was not developed.

Example 5.-10 g. of coupler No. V, 30 g. of organic sulfonic acid No.49, 100 g. of p-phenylphenol, 40 g. of chlorinated rubber, and 3000 g.of benzene were treated in the same manner as in Example 1 to obtain aheat sensitive copying sheet which Was then heated to obtain a blueimage. In case of the omission of the organic sulfonic acid, the colorwas not developed at all.

Example 6.-10 g. of ground coupler No. VI, and 100 g. of acetanilidewere dispersed in a solution of 30 g. of polyvinyl alcohol and 500 g. ofwater. On the other hand, 10 g. of ground organic sulfonic acid No. 29and 50 g. of acetanilide were dispersed in a solution of 15 g. ofpolyvinyl alcohol and 300 g. of water. Both dispersions were mixed andwere treated in a ball mill for hours, and then were coated on a paperand dried to obtain a heat sensitive copying sheet which was then heatedto obtain a blue image. In case of substituting salicyclic acid fororganic sulfonic acid No. 29 (solfosalicyclic acid), the color was notdeveloped.

Example 7.Example 1 was repeated using coupler Nos. VII, VHI, IX and X,respectively, to obtain a blue image.

Example 8. g. of coupler No. X, g. of organic sulfonic acid No. 18, 140g. of benzoic acid, 50 g. of a vinyl chloride-vinyl acetate copolymerand 1500 g. of toluene were mixed and ground in a ball mill for 2 days,and were coated on a paper and dried to obtain a heat sensitive copyingsheet. The sheet was superposed on an original drawing and heated bymeans of a heat sensitive copying machine to obtain a blue imagecoresponding to the characters on the original drawing. Also, the sheetwas treated in the same manner as described above, in the exception ofsubstituting 50 g. of hydroxyethylcellulose and 1500 g. of water forvinylchloride-vinyl acetate copolymer and toluene to obtain the sameresult.

In every case, when an organic sulfonic acid was not used, a coloredimage could not be obtained.

Example 9.-The color development of the respective combination ofcouplers Nos. I to X and organic sulfonic acids Nos. 1 to 60 in the samemanner as in Examples 1 to 8 was blue. However, in using the coupler No.l, the color developed was blue violet, and in using the coupler No.VII, the color obtained first was blue by increasing the amount of anorganic sulfonic acid to be used by about 30% by weight.

What is claimed is:

1. A heat sensitive copying sheet comprising a support having coatedthereon a layer comprising (a) a spiro compound having the Formula A I-O O wherein R and R each is selected from the group consisting of ahydrogen atom, an alkyl group having from 1 to 8 carbon atoms, acarboxylic acid ester, an aralkyl group and a phenyl group, (b) a solidorganic sulfonic acid having the Formula B,

wherein R is selected from the group consisting of an amino group, anN-substituted amino alkyl group having from 2 to 18 carbon atoms, anunsubstituted amino alkyl group having from 2 to 18 carbon atoms, analkyl group having from 10 to 20 carbon atoms, an alkoxy group havingfrom 10 to 20 carbon atoms, an alkyl group substituted with a carboxylicacid group, said alkyl group having from 6 to 18 carbon atoms, an alkylgroup, and an aromatic ring, and (c) a thermofusible material having amelting point ranging from 50 to C., from 1 to 2 parts by weight of thespiro compound being present for every 1 to 6 parts by weight of thesolid organic sulfonic acid.

2. The heat sensitive copying sheet as claimed in claim 1 wherein saidspiro compound is selected from the group consisting of2,2-spirobi-(benzolflchromene), 3-methyl- 2,2'-spirobi( benzo [f 1chromene) 3-isopropyl-2,2'-spirobi- (benzo [f] chromene3-amyl-2,2'-spirobi (benzo [f] chromene),3-octyl-2,2'-spirobi(benzo[f]chromene), 3,3'-dimethyl-2,2-spirobi (benzo[f 1 chromene) 3,3 '-dicarboethoxy-2,2-spirobi (benzo [f chromene3-benzyl-2,2'-spirobi (benzo [f] chromene) 3-phenylethyl-2,2'-spirobi(benzo- [f]chromene), or 3-phenyl-2,2-spirobi(benzo[f]chromene).

3. The heat sensitive copying sheet as claimed in claim 1 wherein saidthermofusible material is selected from the group consisting ofacetoanilide, urea, diphenylamine, diphenyl, naphthalene, benzoin,a-naphthol, fi-naphthol, p-t-butylphenol, p-phenylphenol,4,4'-cyclohexylidine-diphenol, phthalic anhydride, maleic anhydride,stearic acid, benzoic acid, u-naphthyl acetic acid, methylp-hydroxybenzoate, diphenyl phthalate, triphenyl phosphate or p-hydroxydiphenyl ester.

4. A heat sensitive copying sheet comprising a support having coatedthereon a layer comprising (a) a spiro compound having the Formula AIll; R1

wherein R is selected from the group consisting of an amino group, anN-substituted amino alkyl group having from 2 to 18 carbon atoms, anunsubstituted amino alkyl group having from 2 to 18 carbon atoms, analkyl group having from 19 to 20 carbon atoms, an alkoxy group havingfrom 10 to 20 carbon atoms, an alkyl group substituted with a carboxylgroup, said alkyl group having from 6 to 18 carbon atoms, an aralkylgroup, and an aromatic ring, (c) a thermofusible material having amelting point ranging from 50 to 180 C. and which is substantiallycolorless at a temperature lower than 50 C., and (d) a binder, from 1 to2 parts by weight of the spiro compound being present for every 1 to 6parts by weight of the solid organic sulfonic acid.

5. The heat sensitive copying paper as claimed in claim 4 wherein saidbinder is selected from the group consisting of styrene-butadienecopolymers, alkyd resins, polybutyl methacrylates, vinyl chloride-vinylacetate copolymers, styrene-maleic anhydride copolymers, syntheticrubbers, gum arabic, polyvinyl alcohol and hydroxyethyl cellulose.

6. A heat sensitive copying sheet comprising a support having coatedthereon (a) a spiro compound having the Formula A wherein R and R eachis selected from the group consisting of a hydrogen atom, an alkyl grouphaving from 1 to 8 carbon atoms, a carboxylic acid ester, an aralkylgroup and a phenyl group, (b) a solid organic sulfonic acid having theFormula B wherein R is selected from the group consisting of an aminogroup, an N-substituted amino alkyl group having from 2 to 18 carbonatoms, an unsubstituted amino alkyl group having from 2 to 18 carbonatoms, an alkyl group having from 1-0 to 20 carbon atoms, an alkoxygroup having from to carbon atoms, a carboxylic acid substituted alkylgroup, said alkyl group having from 6 to 18 carbon atoms, an aralkylgroup, or an aromatic ring, and (c) a thermofusible material having amelting point ranging from 50 to 180 C., from 1 to 2 parts by Weight ofthe spiro compound being present for every 1 to 6 parts by weight of thesolid organic sulfonic acid.

7. Heat sensitive copying sheets comprising a combination of twosupports, one support having coated thereon a layer comprising (a) aspiro compound having the Formula A Y CCCXXQ wherein R and R each isselected from the group consisting of a hydrogen atom, an alkyl grouphaving from 1 to 8 carbon atoms, a carboxylic acid ester, an aralkylgroup and a phenyl group, and (b) as a coupler, a solid organic sulfonicacid having the Formula B R SO3H (B) wherein R is selected from thegroup consisting of an amino group, an N-substituted amino-alkyl grouphaving from 2 to 18 carbon atoms, an unsubstituted amino alkyl grouphaving from 2 to 18 carbon atoms, an alkoxy group having from 10 to 20carbon atoms, a carboxylic acid substituted alkyl group, said alkylgroup having from 6 to 18 carbon atoms, an aralkyl group, and anaromatic ring, and the other support having coated thereon a layercontaining a thermofusible material having a melting point ranging from50 to 180 C., from 1 to 2 parts by weight of the spiro compound beingpresent for every 1 to 6 parts by weight of the solid organic sulfonicacid.

8. Heat sensitive copying sheets comprising a combination of twosupports, one support having coated thereon a layer comprising (a) aspiro compound having the Formula A,

12 wherein R and R each is selected from the group consisting of ahydrogen atom, an alkyl group having from 1 to 8 carbon atoms, acarboxylic acid ester, an aralkyl group and a phenyl group, and (b) athermofusible material having a melting point ranging from 50 to C., theother support having coated thereon a layer comprising a solid organicsulfonic acid having the Formula B,

wherein R is selected from the group consisting of an amino group, anN-substituted amino alkyl group having from 2 to 18 carbon atoms, anunsubstituted amino alkyl group having from 2 to 18 carbon atoms, analkyl group having from 10 to 20 carbon atoms, an alkoxy group havingfrom 10 to 20 carbon atoms, a carhoxylic acid substituted alkyl group,said alkyl group having from 6 to 18 carbon atoms, an aralkyl group, andan aromatic ring, from 1 to 2 parts by weight of the spiro compoundbeing present for every 1' to 6 parts by weight of the solid organicsulfonic acid.

9. Heat sensitive copying sheets comprising a combination of twosurfaces, one surface having coated thereon a layer comprising a spirocompound having the Formula A,

wherein R and R each is selected from the group consisting of a hydrogenatom, an alkyl group having from 1 to 8 carbon atoms, a carboxylic acidester, an aralkyl group and a phenyl group, the other surface havingcoated thereon a layer comprising (a) a solid organic sulfonic acidhaving the Formula B wherein R is selected from the group consisting ofan amino group, an N-substituted amino alkyl group having from 2 to 18carbon atoms, an unsubstituted amino alkyl group having from 2 to 18carbon atoms, an alkyl group having from 10 to 20 carbon atoms, analkoxy group having from 10 to 20 carbon atoms, a carboxylic acidsubstituted alkyl group, said alkyl group having from 6 to 18 carbonatoms, an aralkyl group, and an aromatic ring, and (b) a thermofusiblematerial having a melting point ranging from 50 to 180 C., from 1 to 2parts by weight of the spiro compound being present for every 1 to 6parts by weight of the solid organic sulfonic acid.

10. The heat sensitive copying sheet of claim 1 wherein thethermofusible material is substantially colorless at a temperature lowerthan 50 C., and is present in an amount of from 3 to 30 weight parts.

11. The heat sensitive copying sheet of claim 4 wherein saidthermofusible material is present in an amount from 3 to 30 weight partsand said binder is present in an amount of from 3 to 15 weight parts.12. The heat sensitive copying sheet of claim 6 wherein saidthermofusible material is substantially colorless at a temperature lowerthan 50 C., and is present in an amount of from 3 to 30 weight parts.

13. Heat sensitive copying sheets as claimed in claim 7 wherein thethermofusible material is substantially colorless at temperatures lowerthan 50 C., and is present in an amount of from 3 to 30 weight parts.

14. Heat sensitive copying sheets as claimed in claim 8 wherein thethermofusible material is substantially colorless at temperatures lowerthan 50 C., and is present in an amount from 3 to 30 weight parts.

15. Heat sensitive copying sheets as claimed in claim 9 wherein thethermofusible material is substantially colorless at temperatures lowerthan 50 C., and is present in an amount from 3 to 30 weight parts.

16. The heat sensitive copying sheet as claimed in claim 1 wherein thelayer further comprises from 3 to 15 weight parts of a binder.

13 14 17. The heat sensitive copying sheet as claimed in claim OTHERREFERENCES 6 wherein the material coated thereon further contains Day:chemical Review VOL 63 1963 65 80 from 3 to 15 weight parts of a binder.(only 65 and 66 Pertinent).

References Cited 5 MURRAY KATZ, Primary Examiner UNITED STATES PATENTS3,293,060 12/1966 Harbort 117-36.9

3,445,261 5/1969 Talvalkar 11736.9' l17l55 UA; 260-3452

